THEORY OF THE EARTH. 105 



does not voluntarily remove far from the places 

 \vhere it finds, in the necessary degree, all that is 

 requisite, for the support of its species, and does 

 not even extend its haunts to any great distance, 

 unless it also finds all these circumstances con- 

 joined. Thus, although the wolf and the fox in- 

 habit all the climates from the torrid to the fri- 

 gid zone, we hardly find any other difference 

 among them, in the whole of that vast space, 

 than a little more or a little less beauty in 

 their fur. I have compared skulls of foxes 

 from the northern countries and from Egypt, 

 with those of the foxes of France, and have found 

 no difference but such as might be expected in 

 different individuals. Such of the wild animals 

 as are confined within narrower limits, vary still 

 less, especially those which are carnivorous. The 

 only difference between the hyena of Persia and 

 that of Morocco, consists in a thicker or a thinner 

 mane. 



The wild herbivorous animals feel the influ- 

 ence of climate somewhat more extensively, be- 

 cause there is added to it in their case, the influ- 

 ence of the food, which may happen to differ both 

 as to quantity and quality. Thus, the elephants of 

 one forest are often larger than those of another ; 

 and their tusks are somewhat longer in places where 

 their food may happen to be more favourable for 

 the production of the matter of ivory. The same 





